Data protection plays an increasingly important role in today's computer systems. Data protection often involves creating regular backups of data. Data may be backed up in various ways, such as by creating a snapshot of a disk. A snapshot, as used herein, includes a backup copy of data as it appeared at a certain point in time. Typically, a portion of disk data is stored in a separate memory associated with the disk, such as in a cache. Before creating a snapshot of a disk, data held in that associated memory is typically flushed to the disk so that a consistent snapshot of the disk can be taken. It would be desirable to have a method for making a disk consistent for file system backup or for other purposes.